/** Apply fill / explicit size to the adapter host and make the engine root fill it. */
export declare function applyCanvasHostBox(container: HTMLElement, root: HTMLElement, opts: {
    fill: boolean;
    width: number;
    height: number;
}): void;
/**
 * Size the adapter host (React/Vue div or custom element) so percentage widths
 * don't collapse when the host is a shrink-wrapped flex child. Root fills the host
 * unless `rootFillsHost` is false (e.g. PhotoAlbum sizes itself via CSS variables).
 */
export declare function applyBlockHostBox(container: HTMLElement, root: HTMLElement, size: {
    width?: number | string;
    height?: number | string;
    rootFillsHost?: boolean;
}): void;
/** Toggle empty-state nodes; author `display:` rules must not override `[hidden]`. */
export declare function setHidden(el: HTMLElement, hidden: boolean): void;
/** Stable JSON key for options, ignoring functions (callbacks). */
export declare function optionsFingerprint(value: unknown): string;
/** True when non-function fields differ (shallow). */
export declare function optionsVisualChanged(prev: Record<string, unknown>, next: Record<string, unknown>): boolean;